On Sun, 2019-12-22 at 23:39 -0800, Andy Lutomirski wrote: > On Fri, Dec 20, 2019 at 11:27 AM John Andersen > <john.s.andersen@xxxxxxxxx> wrote: > > Strengthen existing control register pinning when running > > paravirtualized under KVM. Check which bits KVM supports pinning > > for > > each control register and only pin supported bits which are already > > pinned via the existing native protection. Write to KVM CR0 and CR4 > > pinned MSRs to enable pinning. > > > > Initiate KVM assisted pinning directly following the setup of > > native > > pinning on boot CPU. For non-boot CPUs initiate paravirtualized > > pinning > > on CPU identification. > > > > Identification of non-boot CPUs takes place after the boot CPU has > > setup > > native CR pinning. Therefore, non-boot CPUs access pinned bits > > setup by > > the boot CPU and request that those be pinned. All CPUs request > > paravirtualized pinning of the same bits which are already pinned > > natively. > > > > Guests using the kexec system call currently do not support > > paravirtualized control register pinning. This is due to early boot > > code writing known good values to control registers, these values > > do > > not contain the protected bits. This is due to CPU feature > > identification being done at a later time, when the kernel properly > > checks if it can enable protections. > > Is hibernation supported? How about suspend-to-RAM? > Something is writing to CR4 during resume which is breaking hibernation. Unfortunately I hadn't been able to get my hibernation test working before sending this out. I will investigate. > FWIW, I think that handling these details through Kconfig is the > wrong > choice. Distribution kernels should enable this, and they're not > going to turn off kexec. Arguably kexec should be made to work -- > there is no fundamental reason that kexec should need to fiddle with > CR0.WP, for example. But a boot option could also work as a > short-term option. Given the situation with hibernation. I think I'll implement the kexec discovery Liran suggested, and then investigate the hibernate situation further. Thanks, John
